1. Field of the Invention
This invention relates to a method for the treatment of a solution of tertiary butyl hydroperoxide in tertiary butyl alcohol to be used as a feedstock in a molybdenum catalyzed olefin epoxidation process in order to inhibit precipitation of the molybdenum catalyst during the epoxidation reaction. More particularly, this invention relates to a method for the partial removal of acidic impurities such as formic acid, acetic acid, isobutyric acid, etc., from a solution of tertiary butyl hydroperoxide in tertiary butyl alcohol to be used as a feedstock in an olefin epoxidation process, such as a process wherein propylene is catalytically reacted with tertiary butyl hydroperoxide in solution in tertiary butyl alcohol in the presence of a catalytic amount of a soluble molybdenum compound in order to inhibit precipitation of the molybdenum catalyst during the epoxidation reaction.
More particularly, this invention relates to a method for the pretreatment with calcium hydroxide and/or calcium oxide of a distillation fraction to be used as a feedstock in a molybdenum catalyzed olefin epoxidation process wherein tertiary butyl hydroperoxide is reacted with an olefin, such as propylene, in solution in tertiary butyl alcohol in an epoxidation reaction zone in order to provide propylene oxide and additional tertiary butyl alcohol, the distillation fraction comprising a solution of tertiary butyl hydroperoxide in tertiary butyl alcohol contaminated with acidic impurities such as formic acid, acetic acid, isobutyric acid, etc., the improvement of the present invention comprising the pretreatment of the distillation fraction with an amount of calcium oxide and/or calcium hydroxide sufficient to partially precipitate the acidic impurities and the removal of the precipitate, whereby, when the thus-treated distillation fraction is used as a feed stock in the epoxidation reaction process, the precipitation of the molybdenum catalyst during the epoxidation reaction is substantially inhibited.
2. Background of the Present Invention
When an olefin epoxide, such as propylene oxide, is to be prepared from the corresponding olefin, such as propylene, by reacting the olefin in organic solvent solution with tertiary butyl hydroperoxide in the presence of a soluble molybdenum catalyst, it is conventional practice to prepare the hydroperoxide feedstock by the non-catalytic or catalytic oxidation of isobutane with oxygen in an oxidation reaction zone to provide an oxidation reaction product comprising unreacted isobutane, tertiary butyl hydroperoxide, tertiary butyl alcohol and oxygen-containing impurities.
It is also conventional practice to remove the unreacted isobutane from the initial oxidation reaction product by distillation and to use the remaining distillation product fraction (normally a bottoms fraction) as the feedstock for the molybdenum-catalyzed reaction of an olefin with the tertiary butyl hydroperoxide. This is advantageous because the tertiary butyl alcohol present in the initial oxidation reaction product serves as a solvent for the peroxidation reaction and because the co-product of the peroxidation reaction is tertiary butyl alcohol, derived from the tertiary butyl hydroperoxide reactant. As a consequence, product work-up is simplified because there is no need to use an extraneous solvent. Also, tertiary butyl alcohol is widely used in motor fuels to enhance the octane characteristics of the motor fuels.